This invention relates to a method of repairing end-of-car hydraulic cushioning devices used on railroad cars. More particularly, the present invention is directed to replacing broken or cracked shafts used in such cushioning devices.
End-of-car hydraulic cushioning devices have been used on freight and passenger railroad cars to dampen train action buff and draft forces. Such cushioning devices are known in the art, as represented by U.S. Pat. Nos. 3,589,527 and 3,752,329. The cushioning devices disclosed in these patents, as well as other cushioning devices in use today, utilize a one-piece piston and shaft arrangement to transfer outside coupling forces through a hydraulic fluid-filled housing. As the piston and shaft move through the housing, they displace hydraulic fluid. The fluid is metered through valves and other orifices in the housing to absorb energy.
Each end-of-car hydraulic cushioning device is designed to fit in a center sill pocket at an end of the railroad car. The shaft includes an end normally provided with a spherical bearing which connects to the car body. The housing is connected to the coupler and is slideable within the sill pocket. The housing has metal stops which engage similar limiting stops fixed on the inside of the sill. These engaging stops limit the length of travel of the housing relative to the piston and shaft as buff and draft forces act upon the railroad car coupler, extending and compressing the cushioning device in its center sill pocket location.
Examination and testing of used cushioning devices and center sill pockets have shown that wear experienced in the pockets may impair the functioning of the limit stops. With such wear, as outside buff and draft forces act upon the shaft and piston, the piston will contact other internal parts of the cushioning device, resulting in stress at the connection of the piston and shaft, and at the connection of the shaft and spherical bearing. Depending on the load, the shaft may crack at either connection, eventually leading to complete failure of the device. Where these connections are achieved through heat shrinking or welding, the shaft and piston or bearing may separate, further damaging other internal critical metering features, so that the cushioning device is virtually irreparable.